Many power tools, such as drills, drivers, and fastening tools, have a mechanical clutch that interrupts power transmission to the output spindle when the output torque exceeds a threshold value of a maximum torque. Such a clutch is a purely mechanical device that breaks a mechanical connection in the transmission to prevent torque from being transmitted from the motor to the output spindle of the tool. The maximum torque threshold value may be user adjustable, often by a clutch collar that is attached to the tool between the tool and the tool holder or chuck. The user may rotate the clutch collar among a plurality of different positions for different maximum torque settings. The components of mechanical clutches tend to wear over time, and add excessive bulk and weight to a tool.
Some power tools additionally or alternatively include an electronic clutch. Such a clutch electronically senses the output torque (e.g., via a torque transducer) or infers the output torque (e.g., by sensing another parameter such as current drawn by the motor). When the electronic clutch determines that the sensed output torque exceeds a threshold value, it interrupts or reduces power transmission to the output, either mechanically (e.g., by actuating a solenoid to break a mechanical connection in the transmission) or electrically (e.g., by interrupting or reducing current delivered to the motor, and/or by actively braking the motor). Existing electronic clutches tend to be overly complex and/or inaccurate.
This section provides background information related to the present disclosure which is not necessarily prior art.